This invention relates to transdermal drug delivery devices and more particularly, to a method for protecting such devices from degradation such as that due to hydrolysis and/or oxidation during storage.
The transdermal route of parenteral drug delivery provides many advantages over other administrative routes. Transdermal drug delivery devices, including multilaminates and monoliths, for delivering a wide variety of drugs or other beneficial agents are described in U.S. Pat. Nos. 3,598,122; 3,598,123; 3,731,683; 3,797,494; 4,031,894; 4,201,211; 4,286,592; 4,314,557; 4,379,454; 4,435,180; 4,559,222; 4,568,343; 4,588,580; 4,645,502; 4,698,062; 4,704,282; 4,725,272; 4,781,924; 4,788,062; 4,816,258; 4,849,226; 4,904,475; 4,908,027; 4,917,895; 4,938,759; 4,943,435; 5,004,610; 5,071,656; 5,141,750; 5,342,623; 5,411,740; and 5,635,203, all of which are hereby incorporated in their entirety by reference.
Drugs may also be administered transdermally by iontophoresis, and iontophoretic delivery devices for delivering a wide variety of drugs of other beneficial agents are well known in the art. Iontophoretic devices include a donor electrode assembly which includes a donor electrode and a reservoir containing the beneficial agent to be iontophoretically delivered. The device also includes a counter electrode assembly and an electric power source. Typical devices are disclosed in U.S. Pat. Nos. 3,991,755, 4,141,359, 4,250,878, 4,274,420, 4,640,689, and 4,702,732, for example, all of which are incorporated herein by reference.
One problem associated with the devices of the prior art is degradation of the contents of the device, such as the drugs, permeation enhancers, matrix materials, or other components contained therein. Degradation not only undesirably breaks down these materials, but it also causes discoloration and formation of odors within the pouched system. Devices susceptible to degradation can not be stored for a reasonable amount of time, thus causing practical problems in their distribution.
A solution disclosed in the prior art is to incorporate an antioxidant into the device. For example, U.S. Pat. Nos. 5,028,431 and 5,242,433, hereby incorporated in their entirety by reference, disclose mixing antioxidants such as BHT into the drug formulation of a transdermal drug delivery device due to the unstable nature of the drug to be delivered.
Another solution has been to incorporate a desiccant material within the sealed pouch containing the transdermal drug delivery device. For example, the Climara(copyright) transdermal estradiol system is packaged and sold within a sealed pouch containing a water scavenger to protect against hydrolysis of estradiol. This system is disclosed in U.S. Pat. No. 5,223,261 and the dessicant containing package is disclosed in U.S. Pat. No. 5,698,217, which are hereby incorporated in their entirety by reference.
Transdermal drug delivery systems typically comprise at a minimum a drug reservoir layer covered or surrounded by a backing layer and a release liner. The backing layer may be occlusive or non-occlusive. For example, the Climara(copyright) system comprises a polyethylene backing layer having a low moisture vapor transmission rate (MVTR) of approximately 7-11 g/m2. 24 hr. More open backing layers such as spun laced polyester (Sontara(copyright)) are disclosed in U.S. Pat. Nos. 5,411,750, 5,500,222, and 5,614,211, which are incorporated herein by reference. Other non-occlusive backing layers are disclosed in U.S. Pat. Nos. 3,426,754, 4,638,043, 4,994,278, 5,352,456, and 5,536,263, all of which are hereby incorporated in their entirety by reference.
We have found that even when placed in pouches containing degradation protectants such as antioxidants and desiccants, certain transdermal delivery devices still degrade at rates higher than desirable. Thus, there is a need for improved storage stability of such devices.
As used herein, the term xe2x80x9cdegradationxe2x80x9d refers to any change in any of the device components during storage, for example by hydrolysis and/or oxidation of the drug, permeation enhancers, matrix materials, and any other excipients contained within the device.
As used herein, the term xe2x80x9cdegradation agentxe2x80x9d refers to any agent within the device or pouch which causes an undesirable by-product, such as water and/or oxidizing agents.
As used herein, the term xe2x80x9cdegradation protectantxe2x80x9d refers to any material which protects against degradation of any of the device components such as water scavengers, oxygen scavengers, or combinations thereof.
As used herein, the term xe2x80x9cnon-occlusivexe2x80x9d refers to a material having a moisture vapor transmission rate (MVTR) of not less than 20 g/m2.24 hr.
We have found that many transdermal drug delivery devices contain degradation agents that must be removed or scavenged from the device in order to maintain stability. When impermeable backings are used, the only pathway which these materials can be exposed to the degradation protectant is through the unsealed edges of the device. Diffusion through this pathway is very slow.
According to our invention, we have found that stability of such devices can be considerably improved when stored in pouches containing degradation protectants if the transdermal device uses a non-occlusive backing.
Accordingly, it is an aspect of this invention to provide an improved method for preventing degradation of the components of transdermal drug delivery devices.
It is another aspect of this invention to provide an improved packaged transdermal drug delivery device comprising a transdermal drug delivery device having a non-occlusive backing layer contained within a sealed pouch containing a degradation protectant.
It is another aspect to increase the shelf-life of a transdermal drug delivery device.
It is yet another aspect of this invention to provide improved packaged oxybutynin transdermal drug delivery systems.
The present invention comprises a combination of a transdermal drug delivery device having a non-occlusive backing layer wherein the device is sealed within a pouch containing a degradation protectant. The combination of the non-occlusive backing layer and the degradation protectant within the sealed pouch protects the contents of the transdermal drug delivery device from degradation.